Sleep Studies

The Red King asleep, by John Tenniel for "Through the Looking Glass" by Lewis Carroll. Source: Wikimedia Commons.

Sleep studies are tests that allow doctors to measure how much and how well a person sleeps. They also help show whether sleep problems exist and how severe they are. Sleep studies are important because untreated sleep disorders can increase the risk for high blood pressure, heart attack, stroke, and other medical conditions.

Other Names

Polysomnogram

Rapid eye movement studies

Description

Sleep studies measure the sleep cycles and stages by recording brain waves (EEG), electrical activity of muscles, eye movement, breathing rate, blood pressure, blood oxygen saturation, and heart rhythm. A specially trained observer records data while the person undergoing the sleep study is asleep. The data is later interpreted and used to help with the diagnosis and treatment of sleep disorders.

Why Sleep Studies Are Done

Doctors can diagnose some sleep disorders by asking questions about sleep schedules and habits and by getting information from sleep partners or parents. To diagnose other sleep disorders, doctors use the results from sleep studies and other medical tests.

Types

Four common sleep studies are used to help diagnose sleep-related problems:

Polysomnogram, or PSG

Multiple sleep latency test, or MSLT

Maintenance of wakefulness test, or MWT

Actigraphy

Polysomnogram

A PSG is usually done while staying overnight at a sleep center. A PSG records brain activity, eye movements, heart rate, and blood pressure.

It also records the amount of oxygen in the blood, how much air is moving through the nose while breathing, and chest movements that show whether there is any breathing. In some cases, breathing sounds, including snoring, also are recorded.

The doctor also may use a PSG to find the right setting on a continuous positive airway pressure (CPAP) machine. CPAP is the most common treatment for sleep apnea.

A CPAP machine uses a small pump to gently supply air to the nose or mouth through a special mask. The right setting involves adding just enough extra air to create mild pressure that keeps the airways open while asleep.

If the doctor thinks that sleep apnea exists, he or she may schedule a split-night sleep study. During the first half of the night, sleep will be checked without a CPAP machine. This will show if there is sleep apnea and how severe it is.

If the PSG shows signs that sleep apnea exists, a CPAP machine will be used during the second half of the split-night study. A technician checks breathing using the PSG and adjusts the flow of air through the CPAP mask to find the correct setting.

A PSG also helps doctors:

Adjust CPAP settings after weight loss or gain

Recheck sleep if symptoms return despite treatment with CPAP

Find out how well surgery has worked to correct a sleep-related breathing problem.

Multiple Sleep Latency Test

This daytime sleep study measures how sleepy the patient is. It's typically done the day after a PSG. The patient relaxes in a quiet room for about 30 minutes while a technician checks their brain activity.

The MSLT records whether the patient falls asleep during the test and what types and stages of sleep they are having. Sleep has two basic types: rapid eye movement (REM) and non-REM. REM sleep and non-REM sleep occur in patterns throughout the night.

The test is repeated three or four times throughout the day. This is because the ability to fall asleep also changes throughout the day.

Maintenance of Wakefulness Test

This daytime sleep study measures ability to stay awake and alert. It's usually done the day after a PSG and takes most of the day.

Results may be used to show whether the inability to stay awake is a public or personal safety concern or to check response to treatment.

Actigraphy

This sleep study is done while the patient goes about their normal daily routine. It doesn't require an overnight stay at the sleep clinic.

The actigraph is a simple device that's usually worn like a wristwatch. The doctor may ask the patient to wear the device for several days, except when bathing or swimming.

This test gives the doctor a better idea about sleep habits.

Preparation

Depending on what type of sleep study are being done, patients may need to bring:

Notes from a sleep diary or sleep log

Pajamas and a toothbrush for overnight sleep studies

A comfortable pillow

A book or something to do between testing periods if having a multiple sleep latency test or a maintenance of wakefulness test (MWT)

It may be necessary to stop or limit the use of tobacco, caffeine, and stimulants before having a sleep study. The doctor may ask about alcohol, medicines, or other substances that are being taken and about allergies that exist.

Some medicines may affect sleep patterns. A sleep specialist will help in planning how to take them during and possibly before the test.

A good night of sleep is helpful before the MWT, because it will be necessary to try to stay awake during this test. If being tested as a requirement for a transportation or safety-related job, it may be necessary to take a drug-screening test in addition to the sleep study.

How is a Sleep Study Done?

{{#ev:youtube|jZTzrVGSOvw}}

Sleep studies are painless. Parents can go with their children to a sleep study.

The polysomnogram (PSG), multiple sleep latency test (MSLT), and maintenance of wakefulness test (MWT) are usually done at a sleep center. The room the sleep study is done in may look like a hotel room. A technician makes the room comfortable for the patient and sets the temperature as desired. They can also answer questions about the study.

Polysomnogram

Sticky patches called sensors are placed on the scalp, face, chest, limbs, and a finger. While sleeping, these devices record brain activity, eye movements, heart rate and rhythm, blood pressure, and the amount of oxygen in the blood.

Elastic belts are placed around the chest and abdomen. They measure chest movements and the strength and duration of each exhaled breath.

Wires attached to the sensors transmit the data to a computer in the next room. The wires are very thin and flexible and are bundled together to minimize discomfort. It is possible to roll in any direction.

A technician in another room monitors the recordings as the patient sleeps. He or she fixes any problems with the recordings that occur.

The technician also helps keep the pateint comfortable and disconnects the equipment if they need to go to the bathroom.

When it's time to sleep, the room will be dark and quiet.

If there are signs of sleep apnea, a split-night sleep study may be done. During the first half of the night, the technician records sleep patterns. At the start of the second half of the night, he or she wakes the patient to fit a continuous positive airway pressure (CPAP) mask over the nose and mouth.

The mask is connected to a small machine that gently blows air through the mask. This creates mild pressure that keeps the airways open while sleeping.

The technician checks how the patient is sleeping with the CPAP machine. He or she adjusts the flow of air through the mask to find the setting that's right for them.

At the end of the PSG, the technician helps the patient out of bed and removes the sensors. If having a daytime sleep study, such as an MSLT, some of the sensors may be left on for that test.

Multiple Sleep Latency Test

The MSLT is a daytime sleep study that's usually done after a PSG. Sensors on the scalp, face, and chin usually are used for this test. These sensors record brain activity. They show various stages of sleep and how long it takes to fall asleep. Sometimes breathing is checked during an MSLT.

A technician in another room watches these recordings during sleep. He or she fixes any problems with the recordings that occur.

Starting 1.5 to 3 hours after waking from the PSG, the patient is asked to relax in a quiet room for about 30 minutes. The test is repeated three or four times throughout the day. This is because the ability to fall asleep changes throughout the day.

There will be 2-hour breaks between tests. It may be necessary to stay awake during the breaks.

The MSLT records whether the patient falls asleep during the test and what types and stages of sleep they have. Sleep has two basic types: rapid eye movement (REM) and non-REM. Non-REM sleep has four distinct stages. REM sleep and the four stages of non-REM sleep occur in patterns throughout the night.

The types and stages of sleep can help the doctor diagnose a sleep disorder such as narcolepsy, idiopathic hypersomnia, or a circadian rhythm disorder.

Maintenance of Wakefulness Test

This sleep study occurs during the day. It's usually done after a PSG and takes most of the day. Sensors on the scalp, face, and chin are used to measure while awake or asleep.

The patient sits quietly on a bed in a comfortable position and look straight ahead. Then, they simply try to stay awake for a period of time.

An MWT typically includes four trials lasting about 40 minutes each. If the patient falls asleep, the technician will wake them after about 90 seconds. There are usually 2-hour breaks between trials. During these breaks, patients can read, watch television, etc.

If being tested as a requirement for a transportation- or safety-related job, it may be necssary to have a drug-screening test before the MWT.

Actigraph Test

Patients don't have to go to a sleep center for this study. The actigraph is a small device that's usually worn like a wristwatch. It is possible to go about a normal daily routine while wearing it. It is removed while swimming or bathing.

The actigraph measures sleep-wake behavior over 3 to 7 days. Results give the doctor a better idea about sleep habits. Patients may be asked to keep a sleep diary while wearing the actigraph.

Risks

Sleep studies are painless. There is a small risk of skin irritation from the sensors. The irritation will go away once the sensors are removed.

Expected Outcomes

Once the sensors are removed after a polysomnogram, multiple sleep latency test, or maintenance of wakefulness test, the patient can go home. If using an actigraph to measure sleep-wake behavior, it should be returned it to the doctor's office.

Patients do not receive a diagnosis right away. The primary care doctor or sleep specialist will review the results of the sleep study or sleep studies. He or she will use the medical history, sleep history, and the test results to make a diagnosis.

It may take a couple of weeks to get the results of the sleep study. Usually, the doctor, nurse, or sleep specialist will explain the test results and work with the patient and their family to develop a treatment plan.

Results From a Polysomnogram

For sleep-related breathing disorders, such as sleep apnea, technicians use a PSG to record the number of abnormal breathing events. These include either pauses in breathing or dips in the level of oxygen in the blood.

In adults, when the number of events is 10 or more per hour, treatment may be needed. Children who have one to three events per hour also may need treatment.

Results From a Multiple Sleep Latency Test

MSLT results are used to help diagnose narcolepsy, idiopathic hypersomnia, and circadian rhythm disorders.

For narcolepsy, technicians study how quickly the patient falls asleep. The MSLT also shows how long it takes to reach different types and stages of sleep. Sleep has two basic types: rapid eye movement (REM) and non-REM. Non-REM sleep has four distinct stages. REM sleep and the four stages of non-REM sleep occur in patterns throughout the night.

People who fall asleep in less than 5 minutes or quickly reach REM sleep may need treatment for a sleep disorder.

Results From a Maintenance of Wakefulness Test

Maintenance of wakefulness test (MWT) results may be used to show whether the inability to stay awake is a public or personal safety concern. This study also is used to show how well treatment is working.

Results From an Actigraph Test

Actigraph results give the doctor a better idea about a patient's sleep habits, such as when they sleep or nap and whether the lights are on while they sleep. This study also is used to help diagnose circadian rhythm disorders.

Experts on Sleep Studies

The American Academy of Sleep Medicine has a Sleep Center locator map on their website: Sleepcenters.org.

Research

A recent article outlines the updated parameters for the use of actigraphy in sleep research. [1]

History

According to a recent article in the Journal Sleep Medicine[2], Eduard Robert Michelson (1861-1944) established the first sleep laboratory in 1888. He studied the physiology of sleep and described, for the first time, the periodicity of the sleep cycles.

References

↑ Morgenthaler T, Alessi C, Friedman L, et al. Practice parameters for the use of actigraphy in the assessment of sleep and sleep disorders: an update for 2007. Sleep. 2007 Apr 1;30(4):519-29. Abstract

↑ Weber MM, Burgmair W. "The assistant's bedroom served as a laboratory": Documentation in 1888 of within sleep periodicity by the psychiatrist Eduard Robert Michelson. Sleep Med. 2008 Jul 1. (Epub ahead of print) Abstract

External Links

The basis of this article is contributed from Medpedia.com These articles are licensed under the GNU Free Documentation License It may have since been edited beyond all recognition. But we thank Medpedia for allowing its use.Please discuss further on the talk page.